Hailemariam met with German Chancellor Angela Merkel just days after declaring a six-month state of emergency following a protest movement against his one-party regime, which is accused of marginalising the country's largest ethnic groups.
"We want to reform the electoral system so the voices of those who are not represented can also be heard in the parliament," Hailemariam said.
"Because of this electoral system 51 percent of votes is enough to win all the seats."
His regime currently faces its biggest challenge in the 25 years since coming to power.
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When he succeeded Ethiopia's former Marxist rebel-turned-leader Meles Zenawi, who died in 2012, Hailemariam said he was committed to opening up the country's political system to allow more space for opposition parties.
However international rights organisations regularly criticise his government for cracking down on dissenting voices, keeping a stranglehold on the media and intimidating the opposition during election campaigns.
"Our democratisation process is still nascent. It's fledgling... We want to go further in opening up political space and engagement with civil society groups," said Hailemariam.
"We have been demanding this for several years. They are always promising things for the consumption of the international community but it's never implemented," he told AFP.
"The people are demanding more than what can be done four years from now. They want fundamental changes: a transitional unity government where all stakeholders will be included."
Merkel, who is on a three-nation Africa tour aimed at fighting terrorism and stemming the migrant influx to Europe, told Hailemariam that a "vibrant democracy needs opposition, it needs free media. People want to express their views".